1. Field of the Invention
The present invention relates generally to an electroactive solid-state actuator, and, more particularly, to an electroactive solid-state actuator having a novel single layer structure, which is advantageous because it solves the problem of contact between a conductive polymer and a solid electrolyte.
2. Description of the Related Art
As well known to those skilled in the art, an electroactive actuator refers to an actuator using an electroactive polymer (EAP). The electroactive polymer is advantageous because it has larger variation and smaller density, as well as faster response properties, compared to those of shape memory alloys (SMA) or electoactive ceramics (EAC) as other small actuator materials. Thus, the electroactive polymer is known to have properties most similar to those of natural muscles, and, at present, is vigorously and thoroughly studied for application to various small robot actuators.
In addition, a conventional electroactive actuator which has used a liquid electrolyte has drawbacks, such as limited variation and a low current application range. Thus, in recent years, an electroactive solid-state actuator having a solid electrolyte substituted for the liquid electrolyte has been developed.
Conventionally, an electroactive solid-state actuator comprises a three-layer structure including an electroactive polymer sheet, made of a silicone rubber or an acrylic material, and a pair of compliant electrodes formed on opposite surfaces of the sheet, which is illustrated in FIG. 1.
Referring to FIG. 1, the electroactive solid-state actuator 10 includes a solid electrolyte film 11 and conductive polymer layers 13a and 13b formed on opposite surfaces of the solid electrolyte film 11. As such, the conductive polymer layers 13a and 13b, which are additional layers serving as compliant electrodes, are connected to two electrodes 15a and 15b of a voltage application part 17, respectively.
When the voltage is applied through the two electrodes 15a and 15b, respective conductive polymer layers 13a and 13b are caused to be polar. Further, the cationic component of the solid electrolyte film 11 is shifted to any one conductive polymer layer 13a or 13b as a cathode. Thereby, expansion occurs at the electrolyte portion adjacent to any one conductive polymer layer 13a or 13b, while constriction occurs at the electrolyte portion adjacent to the other conductive polymer layer 13b or 13a. Thus, curvature toward the other conductive polymer layer 13b or 13a takes place. Such actuation can be variously controlled in accordance with the polarity and magnitude of the applied voltage.
The conventional electroactive solid-state actuator 10 basically has a three-layer structure, that is, conductive polymer layer 13a/polymer electrolyte film 11/conductive polymer layer 13b. The three-layer structure is obtained by attaching the conductive polymer layers 13a and 13b to the opposite surfaces of the previously prepared polymer electrolyte film 11. Thus, the attachment process is complicated, and also, contact defects may easily occur. In particular, low adhesive strength may cause undesired detachment due to variation occurring upon actuation, whereby the actuator may become inoperative.
Hence, there is the need for a new technique of manufacturing an actuator having a more stable actuation structure while solving the problems of the three-layer structure of the conventional electroactive solid-state actuator.